If I were to say "Mr. Li is cheerful, healthy, and interesting." It would be リさんはあかるくて、げんきで、おもしろいです。
What I don't understand is how to connect negative adjective sentences, like if I wanna say "Mr. ...

With い adjectives, to conjugate the verb into positive, negative, present or past tense, you change the い to くない, かった or くなかった. But with な adjectives, you conjugate by changing です to ではありません, でした and ...

Tae Kim translates the following as:
他にいいものがたくさんあるけど、やっぱりこれにする。
There are a lot of other good things, but as I thought, I'll go with this one.
Here is 他 a noun, adjective or an adverb? I would think ...

I was just reminded on another site that "being good at something" is expressed as [上手]{じょうず}/[上手]{うま}い, not いい. How do you tell someone they "have gotten better at something"? Xさん, 料理することがもっと上手いですね。 ...